Chris Mason, the Oracle engineer and lead Btrfs developer, began his Btrfs pull request for the Linux 3.2 kernel by saying, "This pull request is pretty beefy, it ended up merging a number of long running projects and cleanup queues."
Among the noteworthy changes to Btrfs in Linux 3.2 compared to Linux 3.1 are many clean-ups and optimizations, scrubber improvements (including performance improvements), error handling fixes, and improved recovery support. There were also some log tree improvements to Btrfs, but they were backed out at the last minute and now a likely candidate for the Linux 3.3 kernel.
The pull request for the Linux 3.2 kernel updates to the Btrfs file-system can be found here. There's 113 Btrfs commits to this kernel's merge window, which touch a total of more than 6,000 lines of code. The Btrfs file-system user-space utilities have been improving too.
Among the benefits of the Btrfs file-system is support for features like checksums, snapshots, space cache, and volume management. There's also fairly nice compression support via LZO and Zlib. The snapshot support in Btrfs allows for features like system roll-backs or quickly finding regressions.
the default file-system in Fedora 17, which is codenamed the Beefy Miracle. Once Fedora adopts Btrfs by default on new installs, it will only be a matter of time before the other tier-one distributions pick this up as the default on new installations. Most distributions for now at least offer Btrfs as an advanced user option on new installs.
Among the other changes for the Linux 3.2 kernel is a Samsung DRM driver, Intel Poulsbo improvements, open-source GPU driver updates, NVIDIA Tegra 3 support, and many staging area changes. The Linux 3.2 kernel will not officially be released until early 2012 due to the tardiness of the release cycle.
Benchmarks of Btrfs, EXT, et al from the Linux 3.2 kernel will be underway.